Optical semiconductor device

An optical semiconductor device, comprising:

• a first semiconductor chip including a light receiving element for receiving optical data in two different formats, first and second signal processing circuits for processing an output signal from said light receiving element, when input data in the first and second communication format is received, respectively, and a driving circuit for driving a light emitting element, said said light receiving element, said first and second signal processing circuits, and said driving circuit being integrated on the same semiconductor substrate;
• a second semiconductor chip in which the light emitting element is disposed;
• a resin sealing body which seals said first and said second semiconductor chips with light receiving and emitting faces of the light receiving and light emitting elements, respectively, oriented upward and is transparent to a prescribed wavelength of light;
• and
• a light reflecting face formed on said resin sealing body and crossing a normal line to a plane of said light receiving and emitting faces at a prescribed angle, wherein a side wall of said resin scaling body serves as the light receiving or emitting face.